In processes for semiconductor device production, silicon wafers are mechanically and chemically polished using a polishing composition. Thereafter, the polished silicon wafers are generally rinsed using water or a rinsing composition such that the silicon wafers are protected from remaining silicon dioxide and metal impurities contained in the polishing composition.
A conventional polishing composition disclosed in Japanese Laid-Open Patent Publication No. 63-272460 contains at least one chelating agent such as ethylenediaminetetraacetic acid (EDTA), and a high molecular ion having a molecular weight of 5000 or more such as polyacrylic acid, in addition to water and particulate amorphous silica. Another conventional polishing composition disclosed in Japanese Laid-Open Patent Publication No. 2001-77063 contains polishing particles, amines such as piperazine, and a chelating agent such as EDTA.
These conventional polishing compositions prevent the silicon wafers from being contaminated by metal impurities contained in the polishing compositions by virtue of the chelating agent that coordinates with a metal element to form a stable complex ion. The chelating agents contained in the conventional polishing compositions, however, do not have a very high capability for capturing metal impurities. Therefore, in the case where semiconductor devices are fabricated from silicon wafers polished using the prior art polishing compositions, poor conditions for semiconductors are often caused due to short circuits or leaks. The silicon wafer contamination caused by metal impurities means not only adhesion of metal impurities on the surface of the silicon wafer but also diffusion of metal impurities in the inside of the silicon wafer.